As Mother’s Day approaches, a UBC expert discusses ‘baby brain’ and other ways that motherhood changes a woman’s brain chemistry

Galea says understanding the long-term effects of motherhood will improve medical care and treatment for mothers.

Are mothers’ brains really different than other women’s?

We all know motherhood changes women’s bodies, but it also changes their brains. Some changes are temporary, but others are permanent. Our research shows that, as a result of these transformations, mothers experience different cognitive abilities and health risks than women without children. They may even react to medication differently.

What are examples of the brain differences?

The most obvious example is size: during pregnancy, a mother’s brain shrinks by up to eight per cent. It bounces back about six months after birth, but clearly this could have some repercussions.

Another example is that while women’s cells are typically all XX female chromosomes, researchers have found male XY chromosome cells in the brains of mothers who’ve had boys. Thus the cells transfer into the mothers’ bodies when the boys are in the womb.

What are the cognitive effects of these changes?

Liisa Galea

We have all heard the term “baby brain.” This refers to the forgetfulness mothers experience in their last trimester and the first months after giving birth. Impaired memory is definitely one result of the brain changes during pregnancy over the short term.

Longer term, motherhood can actually improve brain activities. Testing in rodents suggests that mothers in the longer term score better on memory and multi-tasking than females who have not given birth. It’s like their brain becomes more prepared to deal with the responsibilities of keeping their family safe and organized.

Is there an evolutionary reason for “baby brain?”

Women are relatively vulnerable during pregnancy. They move slower, are more forgetful and have significantly less energy. The “nesting” impulse that women experience may actually help to keep women safe during this crucial period of pregnancy. This certainly makes sense from an evolutionary perspective.

Studies show that the closer pregnant rodents stay to the nest, the more likely they and their offspring will survive as there is less chance of getting eaten by prey or other risks. So this could be the body’s way of reducing exposure to environmental risks and increasing the chances of a successful of birth.

On the other hand, studies suggest mothers are more likely to experience obsessive-compulsive disorders, post-partum depression or psychosis and Alzheimer’s disease, although for the latter the research is early and the effect seems to be mitigated by breastfeeding, genotype and by how many girls versus boys they have.

What exactly causes these differences between mothers and women who have never given birth?

When pregnant, women experience a prolonged spike in hormones, which sparks their physical transformation. For example, estradiol, a form of estrogen, is 200 times the typical level by week 20 of pregnancy and jumps to 1,000 times the normal level in the last few days. This is incredibly taxing on the system, so it makes sense that lasting ramifications result.

Why do you believe mothers need tailored medical treatments?

If mothers’ brains are different than other women’s brains, as our research finds, it means we must embrace greater personalization of medical care – not only for men versus women, but even among women with different life experiences.

For example, a recent study using female rats shows that hormone replacement therapy – which is extremely important for many women – affects maternal brains differently than non-maternal brains.

This gets to the heart of one of today’s greatest scientific problems: approximately 90 per cent of medical research studies at the animal model level have used male rats. Why would we assume that what works in a male rat automatically works in a female patient before testing it on a female rat? One of the big failures of translational studies is that most fail to acknowledge how subjects’ sex, or other unique characteristics, like motherhood, plays a role. We need to do science better.

Liisa Galea is a professor in UBC’s Dept. of Psychology. This interview has been edited and condensed.